(a) Field of the Invention
The invention relates to a novel tetracarboxylic dianhydride and its derivatives and production. Particularly, it relates to a tetracarboxylic dianhydride useful for producing polyimide precursors or polyimides having low thermal expansion and low residual stress and being suitable for preparing photosensitive resin compositions, and relates to the production and derivatives thereof. The polyimide precursors afford the photosensitive resin compositions with good i-line transmissivity, high-speed developability, high resolution and good dimensional accuracy to suit them to the production of interlayer insulating films or surface-protecting films in semiconductor devices.
It also relates to a polyimide precursor and a polyimide with good heat resistance and good i-line transparency, to a resin composition which contains them and is useful for electronic parts such as semiconductor devices or multilayer wiring boards, and to electronic parts.
It also relates to a photosensitive resin composition and its use for forming relief patterns, and to electronic parts. It particularly relates to a negative or positive, photosensitive resin composition, its use for forming relief patterns and electronic parts using it, which has good i-line transmissivity and, on heating, is capable of being into a heat-resistant polyimide polymer suitable for surface-protecting films, interlayer insulating films and others for electronic parts such as semiconductor devices.
(b) Description of the Related Art
A recent tendency in semiconductor industries has been to replace conventional inorganic interlayer insulating materials with highly heat-resistant organic materials such as polyimide resins because of the characteristic advantages that such organic materials offer.
Circuit patterning on semiconductor integrated circuits or printed boards needs various complicated steps, including coating substrate surfaces with resists, exposing predetermined areas, removing unnecessary parts by etching or the like and washing the substrate surfaces. This has raised a desire to new heat-resistant photosensitive materials which can remain as insulating materials on desired areas after formed into patterned resists by exposure and development.
For example, there have been proposed heat-resistant photosensitive materials containing photosensitive polyimides or cyclized polybutadienes as base polymers, and photosensitive polyimides are particularly noted for their good heat-resistance and easy removal of impurities.
The first-proposed photosensitive polyimides comprise a polyimide precursor and a dichromate (Japanese Patent Application Examined Publication No. 49-17374). In spite of their practical photosensitivity and good film formability, they have found no practical use due to poor storage stability and the residual chromium ion in the product polyimides.
It has been proposed to evade these drawbacks by, for example, mixing polyimide precursors with compounds having photosensitive groups (Japanese Patent Application Unexamined Publication No. 54-109828), or by introducing photosensitive groups into polyimide precursors through the reaction of the functional groups of the polyimide precursors with the functional groups of compounds having the photosensitive groups (Japanese Patent Application Unexamined Publication Nos. 56-24343 and 60-100143).
Such photosensitive polyimide precursors, however, suffer from low sensitivity and defective patterns. This is attributable to the main skeleton derived from aromatic monomers, which contributes good heat-resistance and excellent mechanical properties but makes the polyimide precursors themselves absorb light, thereby lowering the transparency to ultraviolet light and hindering effective photochemical reactions in the exposed areas.
In addition, today's high integration on semiconductors requires increasing preciseness in fabrication rule and higher resolution.
To meet these needs, the conventional contact/proximity aligners using parallel light are being replaced by 1:1 projection aligners called mirror projectors, and further by reduction projection aligners called steppers.
Steppers use a monochromatic light, such as a high-power frequency light of ultra-high-pressure mercury-vapor lamps or an excimer laser. Most of the conventional steppers are g-line steppers using a visible light (435 nm wavelength) of ultra-high-pressure mercury vapor lamps, which is called g-line. The increasing preciseness of fabrication rule, however, needs steppers using light of shorter wavelengths, and i-line steppers (wavelength: 365 nm) are taking the place of g-line steppers (wavelength: 435 nm).
Nevertheless, for the above-mentioned reasons, conventional photosensitive polyimide-based polymers designed for contact/proximity aligners, mirror projection aligners and g-line steppers have poor transparency, particularly almost no transparency to i-line (wavelength: 365 nm), and cannot form desired patterns with i-line steppers.
LOC (Lead On Chip system), which is a high-density semiconductor packaging system, needs thicker surface-protecting polyimide films. The thicker the films, the deeper the problem of poor transparency. Therefore, there is a strong desire for photosensitive polyimides which have a high i-line percent transmittance and form polyimide patterns of good profile by exposure with i-line steppers.
On the other hand, as the diameter of silicon wafers to be substrates has increased with the years, there has arisen the problem of larger warp of silicon wafers coated with surface-protecting polyimide films due to the difference between polyimides and silicon wafers in thermal expansion coefficient. This raised another strong desire for photosensitive polyimides which are much less thermally expansive than conventional polyimides. Rigidly structured molecules generally contribute to decreasing the thermal expansion, but aggravate photosensitivity due to their little transparency to i-line. Flexibly structured molecules decrease the stress applied to silicon wafers to decrease warp and can transmit i-line, but cannot afford the good heat-resistance required of polyimide surface-protecting films.
To improve the i-line transmissivity, it has been proposed to introduce fluorine into polyimides (Japanese Patent Application Unexamined Publication No. 8-234433) or to bend the molecule chains of polyimides (Japanese Patent Application Unexamined Publication No. 8-36264). Nevertheless, fluorine-containing polyimides are less adhesive to silicon wafers, and aggravate the reliability of semiconductor elements. The polyimides having bent molecule chains have poor heat-resistance and high thermal expansion coefficient due to the weak mutual interaction of molecules, and aggravate the reliability of semiconductor elements.